This invention relates to the use of olefinic unsaturated imides as processing aids for high temperature polymers.
Previously known polyimide and polyamide-imide resins suffer from their inability to be processed thermally at elevated temperatures. These resins are often characterized by their insolubility and infusibility properties which make them practically impossible to process with conventional plastics processing equipment. As a consequence, the resins are usually handled in the form of their precursor polyamide acids. The precursor materials, while suitable for the preparation of thin films prepared from solution, cannot be handled by autoclaving and press molding techniques without great difficulty. The polyamide acid forms of both the polyimide and polyamide-imide resins undergo cyclization to the imide form during processing, giving rise to poorly consolidated and void filled parts of low mechanical strength.
The unsaturated imide containing fluxes or processing compounds of this invention act as plasticizers for polyimide or polyamide-imide resins containing olefinic unsaturated end groups as well as for the precursor amide acid form of both the polyimide and polyamide-imide resins. These fluxes greatly enhance the flow of these materials and also facilitate the removal of volatile by-products, thereby permitting the preparation of dense, low void content objects of high mechanical strength. These desirable parts can be made using any of the conventional plastic processing methods such as autoclave molding, vacuum bag molding, compression, transfer and injection molding. Another desirable aspect of the invention is that the unsaturated imide fluxes are incorporated into the backbone of the polyimide or polyamide-imide during processing and thus do not volatilize nor exude from the resin to any appreciable extent during processing or in use service.